The invention relates to an electric switch operated by means of direct current comprising a contact system which includes a fixed contact and a switching contact, and an actuating member acting on the switching contact in order to trigger a switching operation between an "off"and an "on"position of the contact system where the contact system is assigned means for extinguishing an arc generated between the fixed contact and the switching contact during the switching operation.
Electric switches of this type are used, in particular, as power switches in electric hand tools. High currents may flow, in the case of electric motors operated by means a direct voltage of, for example, 125 volts, so that, when they are switched off, an arc occurs at the contacts. The occurrence of arcs may lead to the destruction of the switch, which must be prevented in the case of electric tools for safety reasons.
DE-A1-4232975 discloses an electric switch for high currents, which is provided with means for extinguishing an arc. This switch possesses a contact system consisting of a fixed contact and of a switching contact. An actuating member acts on the switching contact in order to trigger a switching operation between an "off" and an "on" position of the contact system. The means, assigned to the contact system, for extinguishing an arc generated between the fixed contact and the switching contact during the switching operation consist of an extension in the manner of an extinguishing lug on the fixed contact. During the changeover from the "on" to the "off" position, an arc which may possibly occur is dragged onto the extinguishing lug by the moving switching contact. After a particular distance between the extinguishing lug and the switching contact has been exceeded, the arc is then extinguished.
The distance which the switching contact covers during the changeover must be of some length, so that the arc can be extinguished. Additional space is required for the extinguishing lug. This switch consequently cannot be employed in some instances of use, in particular when the handles of electric tools are slender. Moreover, in the case of very high direct currents, it may happen that an arc can no longer be extinguished, thus resulting in premature destruction of the switch.
In the case of earth leakage circuit breakers, which are used, for example in house installations, means for the extinguishing of arcs are likewise known. For example, a circuit breaker with a contact system consisting of a fixed contact and of a switching contact is described in DE-C1-4234065. The switching contact is loaded by a spring in the direction of the "off" position and, in the "on" position, is held bearing on the fixed contact by a movable separating element. An actuating member acts via a toggle lever on the separating element, so that, during the changeover from the "on" to the "off" position, the separating element is moved between the switching contact, which then lifts off from the fixed contact due to the action of the spring, and the fixed contact. Any arc which is possibly generated is forced by the separating element into a spark channel and is extinguished there.
In this circuit breaker, the actuating member does not act directly on the switching contact. Instead, the separating element is mechanically coupled to the actuating member in a complicated manner and movement of the separating element ultimately leads to the changeover of the contact system. The contact system provided with the device for arc extinguishing is complicated and involves a high outlay. Due to the complicated mechanical design, it is also susceptible to faults. Moreover, the contact system requires a large amount of space. A contact system which involves such a high outlay therefore provides no pointer to a small switch which can be used in handles of electric tools and which is unsusceptible to faults.